Docs: Add -X option to git-merge's synopsis.
[git/git.git] / Documentation / git-merge.txt
1 git-merge(1)
2 ============
3
4 NAME
5 ----
6 git-merge - Join two or more development histories together
7
8
9 SYNOPSIS
10 --------
11 [verse]
12 'git merge' [-n] [--stat] [--no-commit] [--squash]
13 [-s <strategy>] [-X <strategy-option>]
14 [--[no-]rerere-autoupdate] [-m <msg>] <commit>...
15 'git merge' <msg> HEAD <commit>...
16
17 DESCRIPTION
18 -----------
19 Incorporates changes from the named commits (since the time their
20 histories diverged from the current branch) into the current
21 branch. This command is used by 'git pull' to incorporate changes
22 from another repository and can be used by hand to merge changes
23 from one branch into another.
24
25 Assume the following history exists and the current branch is
26 "`master`":
27
28 ------------
29 A---B---C topic
30 /
31 D---E---F---G master
32 ------------
33
34 Then "`git merge topic`" will replay the changes made on the
35 `topic` branch since it diverged from `master` (i.e., `E`) until
36 its current commit (`C`) on top of `master`, and record the result
37 in a new commit along with the names of the two parent commits and
38 a log message from the user describing the changes.
39
40 ------------
41 A---B---C topic
42 / \
43 D---E---F---G---H master
44 ------------
45
46 The second syntax (<msg> `HEAD` <commit>...) is supported for
47 historical reasons. Do not use it from the command line or in
48 new scripts. It is the same as `git merge -m <msg> <commit>...`.
49
50 *Warning*: Running 'git merge' with uncommitted changes is
51 discouraged: while possible, it leaves you in a state that is hard to
52 back out of in the case of a conflict.
53
54
55 OPTIONS
56 -------
57 include::merge-options.txt[]
58
59 -m <msg>::
60 Set the commit message to be used for the merge commit (in
61 case one is created). The 'git fmt-merge-msg' command can be
62 used to give a good default for automated 'git merge'
63 invocations.
64
65 --rerere-autoupdate::
66 --no-rerere-autoupdate::
67 Allow the rerere mechanism to update the index with the
68 result of auto-conflict resolution if possible.
69
70 <commit>...::
71 Commits, usually other branch heads, to merge into our branch.
72 You need at least one <commit>. Specifying more than one
73 <commit> obviously means you are trying an Octopus.
74
75
76 PRE-MERGE CHECKS
77 ----------------
78
79 Before applying outside changes, you should get your own work in
80 good shape and committed locally, so it will not be clobbered if
81 there are conflicts. See also linkgit:git-stash[1].
82 'git pull' and 'git merge' will stop without doing anything when
83 local uncommitted changes overlap with files that 'git pull'/'git
84 merge' may need to update.
85
86 To avoid recording unrelated changes in the merge commit,
87 'git pull' and 'git merge' will also abort if there are any changes
88 registered in the index relative to the `HEAD` commit. (One
89 exception is when the changed index entries are in the state that
90 would result from the merge already.)
91
92 If all named commits are already ancestors of `HEAD`, 'git merge'
93 will exit early with the message "Already up-to-date."
94
95 FAST-FORWARD MERGE
96 ------------------
97
98 Often the current branch head is an ancestor of the named commit.
99 This is the most common case especially when invoked from 'git
100 pull': you are tracking an upstream repository, you have committed
101 no local changes, and now you want to update to a newer upstream
102 revision. In this case, a new commit is not needed to store the
103 combined history; instead, the `HEAD` (along with the index) is
104 updated to point at the named commit, without creating an extra
105 merge commit.
106
107 This behavior can be suppressed with the `--no-ff` option.
108
109 TRUE MERGE
110 ----------
111
112 Except in a fast-forward merge (see above), the branches to be
113 merged must be tied together by a merge commit that has both of them
114 as its parents.
115
116 A merged version reconciling the changes from all branches to be
117 merged is committed, and your `HEAD`, index, and working tree are
118 updated to it. It is possible to have modifications in the working
119 tree as long as they do not overlap; the update will preserve them.
120
121 When it is not obvious how to reconcile the changes, the following
122 happens:
123
124 1. The `HEAD` pointer stays the same.
125 2. The `MERGE_HEAD` ref is set to point to the other branch head.
126 3. Paths that merged cleanly are updated both in the index file and
127 in your working tree.
128 4. For conflicting paths, the index file records up to three
129 versions: stage 1 stores the version from the common ancestor,
130 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
131 can inspect the stages with `git ls-files -u`). The working
132 tree files contain the result of the "merge" program; i.e. 3-way
133 merge results with familiar conflict markers `<<<` `===` `>>>`.
134 5. No other changes are made. In particular, the local
135 modifications you had before you started merge will stay the
136 same and the index entries for them stay as they were,
137 i.e. matching `HEAD`.
138
139 If you tried a merge which resulted in complex conflicts and
140 want to start over, you can recover with `git reset --merge`.
141
142 HOW CONFLICTS ARE PRESENTED
143 ---------------------------
144
145 During a merge, the working tree files are updated to reflect the result
146 of the merge. Among the changes made to the common ancestor's version,
147 non-overlapping ones (that is, you changed an area of the file while the
148 other side left that area intact, or vice versa) are incorporated in the
149 final result verbatim. When both sides made changes to the same area,
150 however, git cannot randomly pick one side over the other, and asks you to
151 resolve it by leaving what both sides did to that area.
152
153 By default, git uses the same style as that is used by "merge" program
154 from the RCS suite to present such a conflicted hunk, like this:
155
156 ------------
157 Here are lines that are either unchanged from the common
158 ancestor, or cleanly resolved because only one side changed.
159 <<<<<<< yours:sample.txt
160 Conflict resolution is hard;
161 let's go shopping.
162 =======
163 Git makes conflict resolution easy.
164 >>>>>>> theirs:sample.txt
165 And here is another line that is cleanly resolved or unmodified.
166 ------------
167
168 The area where a pair of conflicting changes happened is marked with markers
169 `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
170 is typically your side, and the part afterwards is typically their side.
171
172 The default format does not show what the original said in the conflicting
173 area. You cannot tell how many lines are deleted and replaced with
174 Barbie's remark on your side. The only thing you can tell is that your
175 side wants to say it is hard and you'd prefer to go shopping, while the
176 other side wants to claim it is easy.
177
178 An alternative style can be used by setting the "merge.conflictstyle"
179 configuration variable to "diff3". In "diff3" style, the above conflict
180 may look like this:
181
182 ------------
183 Here are lines that are either unchanged from the common
184 ancestor, or cleanly resolved because only one side changed.
185 <<<<<<< yours:sample.txt
186 Conflict resolution is hard;
187 let's go shopping.
188 |||||||
189 Conflict resolution is hard.
190 =======
191 Git makes conflict resolution easy.
192 >>>>>>> theirs:sample.txt
193 And here is another line that is cleanly resolved or unmodified.
194 ------------
195
196 In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
197 another `|||||||` marker that is followed by the original text. You can
198 tell that the original just stated a fact, and your side simply gave in to
199 that statement and gave up, while the other side tried to have a more
200 positive attitude. You can sometimes come up with a better resolution by
201 viewing the original.
202
203
204 HOW TO RESOLVE CONFLICTS
205 ------------------------
206
207 After seeing a conflict, you can do two things:
208
209 * Decide not to merge. The only clean-ups you need are to reset
210 the index file to the `HEAD` commit to reverse 2. and to clean
211 up working tree changes made by 2. and 3.; `git-reset --hard` can
212 be used for this.
213
214 * Resolve the conflicts. Git will mark the conflicts in
215 the working tree. Edit the files into shape and
216 'git add' them to the index. Use 'git commit' to seal the deal.
217
218 You can work through the conflict with a number of tools:
219
220 * Use a mergetool. `git mergetool` to launch a graphical
221 mergetool which will work you through the merge.
222
223 * Look at the diffs. `git diff` will show a three-way diff,
224 highlighting changes from both the `HEAD` and `MERGE_HEAD`
225 versions.
226
227 * Look at the diffs from each branch. `git log --merge -p <path>`
228 will show diffs first for the `HEAD` version and then the
229 `MERGE_HEAD` version.
230
231 * Look at the originals. `git show :1:filename` shows the
232 common ancestor, `git show :2:filename` shows the `HEAD`
233 version, and `git show :3:filename` shows the `MERGE_HEAD`
234 version.
235
236
237 EXAMPLES
238 --------
239
240 * Merge branches `fixes` and `enhancements` on top of
241 the current branch, making an octopus merge:
242 +
243 ------------------------------------------------
244 $ git merge fixes enhancements
245 ------------------------------------------------
246
247 * Merge branch `obsolete` into the current branch, using `ours`
248 merge strategy:
249 +
250 ------------------------------------------------
251 $ git merge -s ours obsolete
252 ------------------------------------------------
253
254 * Merge branch `maint` into the current branch, but do not make
255 a new commit automatically:
256 +
257 ------------------------------------------------
258 $ git merge --no-commit maint
259 ------------------------------------------------
260 +
261 This can be used when you want to include further changes to the
262 merge, or want to write your own merge commit message.
263 +
264 You should refrain from abusing this option to sneak substantial
265 changes into a merge commit. Small fixups like bumping
266 release/version name would be acceptable.
267
268
269 include::merge-strategies.txt[]
270
271 CONFIGURATION
272 -------------
273 include::merge-config.txt[]
274
275 branch.<name>.mergeoptions::
276 Sets default options for merging into branch <name>. The syntax and
277 supported options are the same as those of 'git merge', but option
278 values containing whitespace characters are currently not supported.
279
280 SEE ALSO
281 --------
282 linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
283 linkgit:gitattributes[5],
284 linkgit:git-reset[1],
285 linkgit:git-diff[1], linkgit:git-ls-files[1],
286 linkgit:git-add[1], linkgit:git-rm[1],
287 linkgit:git-mergetool[1]
288
289 Author
290 ------
291 Written by Junio C Hamano <gitster@pobox.com>
292
293
294 Documentation
295 --------------
296 Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
297
298 GIT
299 ---
300 Part of the linkgit:git[1] suite